Constant-output generator.



E. ROSENBERG.

CONSTANT OUTPUT GENERATOR.

APPLICATION FILED MAY 17, 1907.

1,084,365, Patent-ed Jan. 13, 1914.

M/i/n asses. JnVen/or.

To all whom it may concern.

' UNITED STATES PATENT OFFICE.

7 EMANUEL ROSENBERG, 0E BERLIN, GERMANY.

CONSTANT-OUTPUT GENERATOR.

, Specification of Letters Patent. Application filed Ma 17, 1907. Serial No. 374,294.

Patented Jan. 13, 1914.

" the voltage falls rapidly with increasing ourrent are desirable, and it has been proposed by me jointly with Heinrich Rosenberg in United States Patent- No, 954,468, of April 12, 1910, to secure this result by providing a machine with a constantfield excitation and arranging the commutator brushes and connections in such a manner that the armature current opposes the field magnetization, so'

that the greater thecurrent the weaker the field becomes, and consequently the lowerthe induced .voltage. When such machines are used on circuits in which resistance and current vary widely, it is evident that the conso the machine may be self-exciting and yet ossess similar characteristics as that have een secured heretofore with separate excitation.

My invention consists in so arranging the field magnet that, beginning from a certain point, the armature current, as it increases, produces a proportionately. greater effect than the same current in the field winding. I secure this result in two ways. First, by arranging a portion of the field magnet, for instance, the field poles carrying the coils so that it becomes saturated at a certain value of current; and second, by providing a leakage-path of low reluctance for the armature flux.

My invention will best be understood by reference to the accompanying drawings, in which Figure 1 shows diagrammatically a dynamo electric machine arranged in accordance' with my invention; Figs. 2, 3, 4 and 5 are explanatory diagrams.- Fig. 6 shows the dynamo mounted on a motor car, driven by a prime mover and feeding an electric motor.

In Fig. 1, 1 represents the field magnet, which is provided with poles. The portions of these poles 2 which carry the field coils 3' I are comparatively small, while the pole shoes 4. are comparatively large. armature, which is provided with commutator brushes 6-6 short circuiting the armature on a line displaced 90 electrical degrees from the line of field magnetization. A second set of brushes 7 are displaced 90 electrical degrees from the brushes 6-6 and are connected to the external circuit 8. The field coils 3 are connected in series with the external circuit.

The particular arrangement of brushes which I have shown is the same that has been suggested inthe above mentioned patent for causing the main current of the armature to oppose the field magnetization. The rotation of the armature in the field produces a difference of potential between the brushes 66,which results in a short circuit current flowing through these brushes. This current magnetizes the armature at right angles to the line of field magnetization, and

directly to demagnetize the primary field, so.

that with a constant field magnetization the terminal voltage of the machine will drop rapidly with increase of current.

When the machine is series-wound, as shown in Fig. 1, it is evident, that not only the demagnetizing efl'ect of the armature current, but also the magnetizing effect of the current in the field coils would increase directly with the current in the external circuit, were it not for the special constructlon that I employ, which forms the Sub ect-matter of my invention. In order to prevent the increase of current in the field COllS 3 from producing a proportionately increased 5 represents the magnetization, the field poles on which these are wound are so dimensioned that they become saturated when the current in the coils reaches a certain value, while owing to the large surface of the pole shoes, to their proximity to each other and to the proximity of the field magnet yoke to the pole shoes, a

the currents in the field and armature, first with a machine with moderately saturated iron and moderate leakage-path and second,

with a machine having a fieldmagnet arranged in accordance with my invention.

In the figure the axis 0A represents armature ampere turns, while the axis OF rep- .resents field ampere turns that would be required to balance the armature ampere turns for any given value of current. The straight line 0-9 represents the relations of field and armature ampere turns without saturation and leakage, while the curve 01O represents the relation under the conditions of saturation and leakage shown in, Fig. 1. Up to a certain, point on the curve, the magntizing efiect of the armature and fieldampere turns increases proportionately,

then as the point ofsaturation of the portions of the field poles carrying the field coils is reached, a greater proportionate increase in field ampere turns is required to balance a given increase in armature ampere turns.

By means of the curve 0-10 the machine may readily be designed to give a' maincurrent of any desired value if the external cir- I cuit 8 is short circuited. When the number of turns of the armature has been decided upon and the desired current for the shortcircuit selected, a point 11'may be located on the curve 010 such that the line 11-12 equals the selected armature ampereturns. The field ampere turns will then be equal to 0-12, and consequently it a number of field turns are chosen which bear to the eftective armature turns a ratio. of 0-12 to 1112, the short circuit current of the machine will be that desired, provided that the ohmic resistance can be left out of account. For any smaller current, as, for instance, that current for which the armature ampere turns are equal to the line O13 the field ampere turns would be equal to the line 13-15, and of this only the portion equal to the line 1314 is required to compensate for the armature magnetization. The remaining magnetomotive force, corresponding to the line 1 l15 is available for producing an effective magnetization, resulting in an induced voltage at the armature terminals.

The voltage characteristic of a machine arranged in accordance with my invention is as shown in Fig, 3, in which the abscissas represent current and the ordinates voltage.

Voltage characteristics as Fig. 4C and Fig. 5 may be secured by selecting a material of high residual magnetism for the field magnet andproviding the coils with a suitable number of turns. By arranging a regulating rheostat in shunt to the exciting coil the output of the dynamo and the maximum of the. current can be varied at will.

The curves 3, 4: and 5 have a portion, in

which the voltage varies in nearly inverse The curvev proportion with the current. 7 representing ideal constant output would be a hyperbola. Now one can easily draw two such parallel hyperbolas for slightly different outputs which will contain in the space between them quite a big portion of the drooping part of the dynamo curve. For this portion the dynamo may be called a constant output dynamo. A variation of the outer resistance, within these limits, does practically not affect the output of the dynamo which, in consequence, will be a suitable generator for are lamps, are welding, melting and other purposes.

In Figs. 3, 4 and 5 I have shown the curves extending below the horizontal axis. This means that-if the current is in some manner increased above the value which was selected as the short-circuit current-in the design of the machine, theinduced voltage at the armature terminals will be reversed. Consequently, if such a'machine is used as a booster, it will give a positive voltage up to a certain current-value, and a negative voltage for currents above that value.

The dynamo can be used also as a generator in vehicles with electric transmission of the driving power in order to avoid an overloading of the prime mover and to develop automatically a lower voltage when the current grows in climbing hills. In Fig. 6 a motor car 21 is shown with electric motor 22 driving the wheels 23, the electric motor, in series with the coils 3 3 of the dynamo, receiving current trom the brushes 7 7 of the dynamo, the other brushes 6 6 being short-circuited. The field magnet 24 is here designed in the manner of the old 1,084,8 66 m l i 8 means, it is possible to vary the input of the motors and even to stop the car without touching the main circuit.

Itwill be'seen that I have illustrated In invention diagrammatically for the sake of simplicity, and consequently I do not desire to limit my,self to the particular construction and arrangement of parts here shown, but aim in the appended claims tocover all modifications which are within the scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a dynamo electric machine, a serieswound fieldmagnet having a portion arranged to be saturated by a fraction of full load current, an armature provided with a commutator, and commutator brushes positioned' to produce, with the armature windings, circuits in which the current ,op poses the field magnetization.

2. In a dynamo electric machine, a serieswound field magnet structure, an armature provided with a commutator,.and commutator brushes positioned toproduce, with the armature windings, circuits in which the current opposes thefield magnetization, the said field magnet structure comprising a yoke, massive pole pieces having a path of low reluctance for the armature flux, and connecting portions between the yoke and the pole pieces, the said connecting portions being so reduced in cross section as to be-' come saturated by a fraction of fullload current. y

3. In a d namo electric machine, a serieswound fiel magnet structure, an armature provided 'with a commutator, and connnu: tator brushes and connections short-circuiting the armature on a line displaced 9O electrical degrees from the line of field magnetization; and a second set of brushes displaced 90 electrical "degrees from the first set. and connected to an external circuit, the

said field magnet structure comprising a yoke, massive pole pieces, having a path of low reluctance for the armature flux, and

connecting portions between the yoke and pole pieces, said connecting portions being so reduced in cross section, as to become saturated by a fraction of full load current.

4. In a dynamo-electric machine, a serieswound field magnet having a portion arranged to be saturated by a fraction of full load current, an armature provided with a commutator, and commutator brushes positioned toproduce, with the armature winding, circuit in which the current op- .poses the field magnetization, the field magnet having a' leakage-path of low reluctance for the armature flux.

5. In a dynamo-electric machine, a serieswound field magnet having a portion ar ran ed to be saturated by a fraction of fullloa current, an armature provided with a commutator, commutator brushes and confrom the line of field magnetization, and a 1 second set of brushes displaced ninety electrical degrees from the first set and connected to the series coil and an external circuit, the field magnet having a leakagepath of low reluctance for the flux produced by the current passing through the second set of brushes.

6. In a dynamo-electric machine, a serieswound field magnet having a portion arranged to be saturated by a fraction of fullload current, an armature provided with a commutator, commutator brushes and connections short-circuiting the armature on a line displaced ninety electrical degrees from the line of field magnetization, and a second set of brushes displaced ninety electrical degrees from the'first set and connected to the series coil and an external circuit.

7. In a dynamo-electric machine, a field magnet having a portion arranged to be saturated by a'fraction of full load current, a series coil on the field magnet, a regulating rheostat in parallel to the series coil, an armature provided with a commutator,

commutator brushes and connections shortcircuiting the armature on a line displaced ninety electrical degrees from the line of field magnetization, and a second set of brushes displaced ninety electrical degrees from the first set and connected to the series coil and an external circuit, the field mag.-

net having a leakage-path of low reluctance for the flux produced by the current passing through the second set of brushes.

8. In a dynamo-electric machine, a serieswound field magnet having a portion arranged to be saturated bya fraction of fullload current, am armature provided with a commutator, commutator brushes and connections short-circuiting the armature on a line displaced ninety electrical degrees a second set of brushes displaced ninety electrical degrees from the first set and connected to the series coil and to an electric motor.

9. A series-wound dynamo-electric machine having means for reducing the pro-' portionate magnetizing fl'ect of the series field winding as the current therein increases, an' armature with a commutator, commutator brushes andconnections shortcircuiting the armature on aline displaced 90 electrical degrees from the line of field 1 magnetization, and a second set of brushes displaced 90 electrical degrees from the first set and connected to the said series-winding and to an external circuit.

10. In a dynamo electric machine, a field magnet having a portion arranged to be saturated bya fraction of'full load, a series from the line of field magnetization, and

exciting "coil on the field magnet connected connected to the series coil'and to an exin parallel to a regulating rheostat an armaternal circuit. 10 ture provided with a commutator, commu- In Witness whereof, I have hereunto set tator brushes and connections short circuitmy hand this second day of May, 1907.

ing the armature on a line displaced 9O elec- EMANUEL ROSENBERG. trical degrees from the line of field magneti- W itnesse s: V zation, and a second set of brushes displaced; JEAN VEmssI,

electrical degrees'froin the first set and PAUL HEINRICH. 

